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  1. #1
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    Default VN heads combustion chamber CC - what's possible?

    Forgive me, for I am noob...

    Have heads off 355 stroker I purchased to rectify leaking gaskets, trying to work out what this thing is capable of and its intended use was while apart.

    Firstly, some info:

    Cast VN heads (not VT)
    Some porting apparent... seems 'a fair bit' to untrained eye.
    Scat crank
    Bore +30 thou
    Keith Black flat top pistons. Think relief is 5cc.
    5.7" rods
    Dodgy piston to deck measurement = 034" (seems reasonable but aimed at low comp?)
    Unknown hydraulic flat tappet cam, lift measured ~285"
    1.65 ratio YT roller rockers with dual valve springs
    O-ringed block, reliefs in heads, ~050" copper head gaskets
    Redline single plane Hiwinder manifold and 750 mech sec Holley


    First question:

    Had a go at guestimating combustion chamber volume.

    Syringe, prepsol, spirit level on head.... got 54cc into chamber before overflow.
    Stock = 63cc or thereabouts as far as I have read.

    Is 54cc possible?


    Second question:

    Getting wildly different answers when trying to calc comp ratio.
    Can do maths, built calc in excel.
    Also tried half a dozen online calcs, results highly variable.
    Amongst them this one was referenced on Aussie V8s a few times so let's run with that for now (Engine Compression Ratio (CR) Calculator ).

    Engine
    Bore 4.03"
    Stroke 3.48"
    Gasket bore 4.1"
    Gasket thickness .050"
    Piston dish 5cc (guess)
    Piston to deck .034"(rough measurement)

    With 64 cc CC, comp ratio = 10.5 (reasonable)

    With 54cc CC, comp ratio = 11.9 (outrageous)


    However, plugging same numbers into spreadsheet which divides swept volume by chamber + gasket + deck clearance I get 8.5 and 9.5 respectively.

    Now, those numbers I calc'd with my spreadsheet and the o'ringed block has me thinking my calcs are correct and this engine was intended for boost.

    But (some) online calcs suggest engine built for stout'ish N/A street application.

    Cam is out and going to doctor to shine further light on what this thing was meant to do.

    All thoughts and comments on cc volume and engine in general very much welcome.

    Damn that hurt my head,
    Shayne.

  2. #2
    casual poster BasicQ's Avatar
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    Is your excel = swept volume+chamber+gasket volume+piston cc’s / chamber+gasket volume+deck clearance+piston cc’s?

  3. #3
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by COM081 View Post
    .............................

    Damn that hurt my head,
    Shayne.
    and so say the rest of us....
    __________________________________
    ONE OF THE Aussie V8 MODERATOR/ADMIN TEAM

    Never late in an AussieV8!
    Club circuit racing...the best fun you can have with your pants on

  4. #4
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    Come on Smitty, focus . .. .need all the help I can get here! It's 2020, we're all in this together

    Is it possible a VN head has been milled and can operate at somewhere near 54cc? I can appreciate that's a 'how long is a piece of string' type question but nevertheless....

    Alright BasicQ, my formula was incorrect. Thank you.

    Is there a quick explanation as to why deck clearance is not included in initial volume? Seems all volumes should be top and bottom of that equation except swept volume, which obviously is not on the bottom? Swept volume is the only thing that changes through the stroke?

    Corrected formula gives 9.3 comp with 64cc head and 10.4 with the 'probably incorrect' 54cc head. .... which is still a fair way off the online calc here: (Engine Compression Ratio (CR) Calculator )
    Last edited by COM081; 26-08-2020 at 11:21 AM.

  5. #5
    Not the Kingswood! hq308's Avatar
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    Using your figures on the Summit calculator comes up with 10.48 for the 54cc chamber

    https://www.summitracing.com/newsand...ion-calculator

  6. #6
    Senior Member 46Crab's Avatar
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    Default VN heads combustion chamber CC - what's possible?

    That engine combo is an ass about way of getting some compression.

    I certainly wouldn’t build a 355 that way to get some compression...
    Last edited by 46Crab; 26-08-2020 at 06:07 PM.

  7. #7
    casual poster BasicQ's Avatar
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    Quote Originally Posted by COM081 View Post





    Is there a quick explanation as to why deck clearance is not included in initial volume? Seems all volumes should be top and bottom of that equation except swept volume, which obviously is not on the bottom? Swept volume is the only thing that changes through the stroke?

    Corrected formula gives 9.3 comp with 64cc head and 10.4 with the 'probably incorrect' 54cc head. .... which is still a fair way off the online calc here: (Engine Compression Ratio (CR) Calculator )
    Sorry deck clearance should be in there as it’s additional cylinder volume to the stroke. Swept volume + everything above it / everything above it = CR

  8. #8
    Do you ever leave? EH179's Avatar
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    That .034" ptd combined with an .050" gasket is going to be a headache.

  9. #9
    Senior Member 46Crab's Avatar
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    Quote Originally Posted by EH179 View Post
    That .034" ptd combined with an .050" gasket is going to be a headache.
    Agree

  10. #10
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    ^^Yup. If you want 10.5-1 you still want zero deck and adj the comp down with a dish in the pistons to suit the chamber volume.

  11. #11
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    Yeah thanks fellas, I'm realising this. Need to confirm measurements but things are pointing in the wrong direction.

    Does milling block to get rid of o-rings and copper gaskets, new pistons to achieve zero deck, cam to suit remaining components seem a reasonable course of action?

    Would heads need to be milled to the extent of removing o-ring relief?

    Quote Originally Posted by BasicQ View Post
    Swept volume + everything above it / everything above it = CR
    Very eloquent. Fairly plain to see that I'm new to this and that's about the perfect explanation for me. Thanks.

  12. #12
    casual poster BasicQ's Avatar
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    Any stampings on the back of the cam such as logo or part number?

    ~.285” lobe lift will only net ~.470” valve lift.

    Interesting if your measurements are accurate with lobe lift to have a cam of that lift and the effort gone to with o-ringing what exactly this combos intentions were? Lift does not directly correlate to duration but that short of lift would suggest short duration, something in the 2teens at .050”. This is speculation though with your preliminary measurements of roughly .285”

    Again, speculation with what you report as rough measurements but as EH179 eluded to an .084” quench height someone either knew what they were doing regarding quench for application or didn’t consider it as part of the build.

    I took a look at a Redline Hiwinder too and it looks like a single plane compromised for bonnet clearance. Someone needed to keep all of this engine under the bonnet.

    I am interested to know what you find as you delve deeper.

  13. #13
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    Quote Originally Posted by COM081 View Post
    Does milling block to get rid of o-rings and copper gaskets, new pistons to achieve zero deck, cam to suit remaining components seem a reasonable course of action?

    Would heads need to be milled to the extent of removing o-ring relief?
    I am probably missing something here, but why would you want to discard the copper head gasket and o-ring/receiver groove if you already have them.

    I would guess this thing was originally blown and made some power, I would personally keep it.

    With the copper you still have the important fuse, MLS not so much.

  14. #14
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    Quote Originally Posted by BasicQ View Post
    I took a look at a Redline Hiwinder too and it looks like a single plane compromised for bonnet clearance. Someone needed to keep all of this engine under the bonnet.

    I am interested to know what you find as you delve deeper.
    Yes that's right. As far as I know the engine was under an early Commodore bonnet, which is also what I'll run it in. Fits with a 1" spacer, 2" may fit too.

    Setup does seem incongrous to my untrained eye, has me thinking intention was forced induction perhaps.

    Pulled cam out last night. Stamped with a logo that looks similar to the Chev logo. Had a three-letter casting on it - CW something... I've forgotten the third letter. Googled it, no hits.

    Cam is now with Camtech to measure specs, fella there reckons lobes look worn. Odd because rest of engine looks fresh enough.

    Intentions at this stage are to get accurate measurements of piston-deck clearance, piston volume and cc volume. If comp ratio turns out to be somewhere near 10.5 I'll get cam to suit, bolt heads back on with new copper gaskets received this week from Ridgecrest and see how it goes.

    If comp ratio is sad I'll look to remedy with the bottom end... I think?

    If piston to deck is 034" as initial measurement suggests then would simply decking the block not do the trick? Plenty of room there to remove o-ring grooves and achieve zero deck.

    Folks have said above to deck block then choose pistons to suit... could I not just have block milled correct amount to achieve same result, all else being equal?

    That aside, if going to more orthodox head gaskets, would the o-ring receiver grooves need to be milled from the heads? I'm assuming yes.

    Appreciate all responses. Thanks, Shayno.
    Last edited by COM081; 27-08-2020 at 12:30 AM.

  15. #15
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    Sorry HQ, response out of sequence.

    Engine is apart because copper gaskets leaked. Seems to be a bit of an issue getting them to work properly? Getting different advise about using sealant, where to use it etc.

    Again to the uninitiated, seems to add complexity that's not required for what I'd hope might be a 350-400HP Sunday squirt engine.

    Happy to be schooled otherwise. Really just looking for least-fuss way to get to that reasonably humble goal.

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